(1) Field of the Invention
The present invention relates to a method of coating adhesive for mounting parts onto a printed substrate incorporated in an automatic mounting device for electronic parts and apparatus therefor, and more specifically, to a method of coating adhesive for mounting parts and apparatus therefor which can be applied to temporary mounting before final mounting by soldering in which chipped electronic parts (hereinafter referred to as chip part), for example, such as resistors, capacitors or transistors are positioned and mounted on a printed substrate.
(2) Prior Art
In the conventional automatic mounting device for electronic parts of this kind, a plurality of multiphase printed substrates are placed on an X-Y table controlled to be moved in an X-Y direction at fixed intervals, a plurality of adhesive coating nozzles corresponding to these printed substrates are arranged, said coating nozzles being selectively synchronized, adhesive within an adhesive storing tank is coated in position on each of the printed substrates before a chip part to be positioned and supplied by a part supplying device is mounted, and a chip part to be positioned and mounted on each of the printed substrates from the part supplying device is temporarily mounted.
In the existing circumstances, however, for the conventional coating devices for adhesive for mounting parts on the printed substrate, particularly for coating nozzles, large-diameter nozzles in which the amount of coating adhesive per coating operation is large and small-diameter nozzles in which the amount of coating adhesive is small are selectively used.
Therefore, in the above-described conventional coating apparatus, there poses no problem for the case of the coating nozzle which intermittently carry out the coating operation of adhesive to the printed substrate; but in the case of the other coating nozzles which are left unused for a long period of time, the adhesive within the storage tank trickles from the tip of the nozzle, which is a so-called "liquid-drip", and if in that state, coating operation of adhesive to the printed substrate is carried out, the adhesive in the amount more than as needed becomes coated on the printed substrate, which is prone to occurrence of unevenness in quality.
Also, a conventional coating nozzle has been proposed as disclosed in Japanese Patent Publication No. 61-56,638 Specification published in Japan, in which a projection is formed on a coating head, adhesive being supplied in advance from a storage tank is held on the end of the projection, and when the coating head is moved onto the printed substrate to carry out the coating operation, the adhesive held on the end of the projection is transferred between connection lands of the chip part on the printed substrate.
However, in such a coating nozzle as described above, both ends and a part of the side on the back side of the chip part may be held by adhesive but the central portion on the back side thereof cannot be held by adhesive because the adhesive is not coated thereon, whereby temporary mounting of the chip part not only becomes unstable but the adhesives are coated on the printed substrate in a spaced apart relation, and therefore if the coating amounts of adhesives are different from each other, mounting becomes unbalanced.